Tropospheric Ozone Variability during the East Asian Summer Monsoon as Observed by Satellite (IASI), Aircraft (MOZAIC) and Ground Stations
Résumé
Satellite measurements from the thermal Infrared Atmospheric Sounding Interferometer
(IASI), the Measurements of OZone and water vapor by in-service AIrbus airCraft
(MOZAIC), as well as observations from ground based stations, are used to assess the
tropospheric ozone (O3) variability during the East Asian Summer Monsoon (EASM).
Six years [2008-2013] of IASI data analysis reveals the ability of the instrument to detect
the onset and the progression of the monsoon reflected by a decrease in the tropospheric
[0-6] km O3 column due to the EASM, and to reproduce this decrease from one year to
the other. Focusing on the period of May-August 2011, taken as an example year, IASI
data show clear inverse relationship between tropospheric [0-6] km O3 on one hand and
meteorological parameters such as cloud cover, relative humidity and wind speed, on the
other hand. Aircraft data from the MOZAIC project at Hyderabad, Nanjing and
Guangzhou are used to validate the IASI data and to assess the effect of the monsoon on
the vertical distribution of the tropospheric O3 at different locations. Results show good
agreement with a correlation coefficient of 0.74 between the [0-6] km O3 column derived
from IASI and MOZAIC. The aircraft data show a decrease in the tropospheric O3 that is
more important in the free troposphere than in the boundary layer and at Hyderabad than
at the other two Chinese cities. Ground station data at different locations in India and
China show a spatiotemporal dependence on meteorology during the monsoon, with
decrease up to 22 ppbv in Hyderabad, and up to 5 ppbv in the North China Plain.